Philonthus Stephens, 1829

Chani-Posse, Mariana, 2010, Revision of the southern South American species of Philonthus Stephens (Coleoptera: Staphylinidae) 2595, Zootaxa 2595, pp. 1-70 : 6-7

Genus Philonthus Stephens

General remarks. The most recent and complete description of the genus, at least for America north of Mexico, is available in Smetana (1995). Some characters of Philonthus are also discussed in Schillhammer (2000a) and Smetana and Davies (2000).

Recognition of the southern South American species. According to Smetana (1995), the genus can be recognized by the combination of the following characters: maxillary palpus with last segment longer than preceding segment, more or less fusiform, never subulate; labial palpus with segment 2 not swollen, segment 3 at least 1.5x as long as penultimate segment; dorsal surface of all tarsal segments glabrous except for scattered, long marginal setae; front tarsus shorter than front tibia, first segment distinctly shorter than segments 2 and 3 combined; first three or four segments of front tarsus in both sexes at least slightly dilated, with at least some modified pale setae ventrally; superior line of pronotal hypomeron not turning downwards until close to front angle, so that lateral puncture of pronotum, bearing long seta, situated close to it and separated from it by distance not larger than diameter of puncture; sternum 9 of male genital segment with proximal portion reduced, asymmetrical, and with distal portion not modified, usually variably emarginated.

Regarding southern South American species, including some of those occurring in other regions, the only characters to be modified from Smetana´s list are the front tarsus as long as to shorter than front tibia, and the first tarsal segment as long as to shorter than tarsal segments 2 and 3 combined. In any case it must be noted that these characters are continuous, and as such, may give ambiguous results when discretized by different authors.

Other characters common to all or most southern South American species are: maxillary palpus with segment 2 longer than segment 3; labial palpus with last segment fusiform and not distinctly narrower than preceding segment; posterior arms of gular sutures running close to each other until the base of head and not joined before neck; styli of tergum 9 simple, moderately stout with exception of those of P. lynchi ; sternum 8 with two long subapical macrosetae at each side with exception of that of P. politus .

Immature stages. The immature stages of the species of Philonthus were discovered very early but their knowledge is very fragmentary and lags greatly behind that of the adults ( Smetana 1995). Nearly all studies of Philonthus immatures have been done for Palaearctic species ( Pototskaya 1966; Kasule 1970; Boller 1983; Kranebitter & Schatz 2002; Staniec & Pietrykowska 2005, 2007; Pietrykowska-Tudruj & Staniec 2006, 2008), with some few exceptions (i.e. Byrne 1993; Hu & Frank 1995; Chani-Posse 2006). In the Nearctic region, only 19 of 112 species here recorded are known as larvae, 16 of which also occur in Europe ( Smetana 1995) and another three also in South America. Concerning America south of Mexico, only eight of the 198 species of Philonthus currently cited are known as larvae (Chani-Posse 2006). I refer the reader to all these papers for a characterization of the immatures stages.

Habitat. The species of Philonthus , as those of other related genera of Philonthina , are considered general predators, or predators favouring Diptera larvae ( Smetana 1995). According to Coiffait and Sáiz (1968), Smetana (1995), Navarrete-Heredia et al. (2002) and information on the specimen labels, they are found in decaying organic materials, such as carrion, dung, rotting tissues, logs, also in association with ants ( P. hepaticus and P. quadraticeps ), in litter and under stones, near streams, in sandy or gravel banks of rivers and creeks, on floor of temperate forests ( Nothofagus spp. , Araucaria spp. ), subtropical and tropical subdeciduous forests, woodlands, compost and cut grass piles, in open forests and forest edges. Specimens have been collected in flight intercept traps, carrion and dung baits or by fogging. Trapping data suggest that species are attracted to UV light. Some species ( P. flavolimbatus , P. rectangulus , P. longicornis ) have been shown to be important predators of immature flies, and their ability and/or potential to reduce populations of dungbreeding flies has been well documented in North America (e.g. Harris & Oliver 1979; Roth 1982; Hunter et al. 1986; Fincher & Summerlin 1994; Hu & Frank 1997) and South America ( Cabrera-Walsh & Cordo 1997; Guimarães & Mendes 1998; Koller et al. 2002; Cabrera-Walsh & Chani-Posse 2003).

Distribution. At present Philonthus is represented by a large number of species in all zoogeographical regions. Concerning southern South America it is interesting to note that most of the species occur in the Neotropical region, and the number of species tends to decrease southwards to the South American transition zone and the Andean region. Among the seven species of Philonthus currently cited for the Andean region, only two of them ( P. bonariensis and P. rubromaculatus ) are native species, the rest are either cosmopolitan ( P.discoideus , P. longicornis and P. varians ) or introduced species ( P. rectangulus and P. politus ).